UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)*

AVROBIO, Inc.

(Name of Issuer)

Common Stock, $.0001 par value per share

(Title of Class of Securities)

05455M100

(CUSIP Number)

Robert Liptak

Clarus Ventures, LLC

101 Main Street, Suite 1210

Cambridge, MA 02142

(617) 949-2200

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

May 20, 2019

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

This Amendment No. 2 (“Amendment No. 2”) to the statement on Schedule 13D amends and supplements the initial statement on Schedule 13D originally filed by Clarus Lifesciences III, L.P. and certain other reporting persons on July 5, 2018, as amended by Amendment No. 1 thereto filed on January 15, 2019 (as amended, the “Schedule 13D”), relating to the Common Stock, par value $0.0001 per share (the “Common Stock”), of AVROBIO, Inc. (the “Issuer”). The address of the principal executive offices of the Issuer is One Kendall Square, Building 300, Suite 201, Cambridge, MA 02139.

Certain terms used but not defined in this Amendment No. 2 have the meanings assigned thereto in the Schedule 13D. Except as specifically provided herein, this Amendment No. 2 does not modify any of the information previously reported in the Schedule 13D.

Item 2 of the Schedule 13D is hereby amended and restated as follows:

This statement is being filed by:

(a) Clarus Lifesciences III, L.P. (the “Fund”);

(b) Clarus Ventures III GP, L.P. (“Clarus GP”), which is the sole general partner of the Fund;

(c) Blackstone Clarus III L.L.C., which is the sole general partner of Clarus GP, Blackstone Holdings II L.P., which is the sole member of Blackstone Clarus III L.L.C., Blackstone Holdings I/II GP Inc., which is the sole general partner of Blackstone Holdings II L.P., The Blackstone Group L.P., which is the controlling shareholder of Blackstone Holdings I/II GP Inc., and Blackstone Group Management L.L.C. (collectively, with Blackstone Clarus III L.L.C., Blackstone Holdings II L.P., Blackstone Holdings I/II GP Inc. and The Blackstone Group L.P., the “Control Entities”), which is the sole general partner of The Blackstone Group L.P. and which is wholly-owned by Blackstone’s senior managing directors and controlled by its founder, Stephen A. Schwarzman.

The persons named in this Item 2 are referred to individually herein as a “Reporting Person” and collectively as the “Reporting Persons.” The Reporting Persons have entered into a Joint Filing Agreement, dated as of the date hereof, a copy of which is filed with this Schedule 13D as Exhibit 99.1 (which is incorporated herein by reference), pursuant to which the Reporting Persons have agreed to file this statement jointly in accordance with the provisions of Rule 13d-1(k) under the Act.

The address of the principal business office of the Fund and Clarus GP is Clarus Ventures, 101 Main Street, Suite 1210, Cambridge, MA 02142. The address of the principal business office of each of the Control Entities and Mr. Schwarzman is c/o The Blackstone Group L.P., 345 Park Avenue, New York, NY 10154.

The principal business of the Fund is to invest in and assist early-stage and/or growth-oriented businesses in healthcare and life sciences. The principal business of Clarus GP is to act as the sole general partner of the Fund.

The principal business of Blackstone Clarus III L.L.C. is performing the functions of, and serving as, the general partner of Clarus GP. The principal business of Blackstone Holdings II L.P. is performing the functions of, and serving as, a managing member (or similar position) of and member or equity holder in Blackstone Clarus III L.L.C. and other affiliated Blackstone entities. The principal business of Blackstone Holdings I/II GP Inc. is performing the functions of, and serving as, the general partner (or similar position) of Blackstone Holdings II L.P. and other affiliated Blackstone entities. The principal business of The Blackstone Group L.P. is performing the functions of, and serving as, the controlling shareholder of Blackstone Holdings I/II GP, Inc., and in a similar capacity for other affiliated Blackstone entities. The principal business of Blackstone Group Management L.L.C. is performing the functions of, and serving as, the general partner of The Blackstone Group L.P. The principal occupation of Mr. Schwarzman is serving as an executive of Blackstone Group Management L.L.C.

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

The Fund, Clarus GP, Blackstone Holdings II L.P. and The Blackstone Group L.P. are limited partnerships organized under the laws of the State of Delaware. Blackstone Clarus III L.L.C. and Blackstone Group Management L.L.C. are limited liability companies organized under the laws of the State of Delaware. Blackstone Holdings I/II GP Inc. is a corporation organized under the laws of the State of Delaware. Mr. Schwarzman is a United States citizen.

Item 5 of the Schedule 13D is hereby amended and restated as follows:

Clarus GP is the sole general partner of the Fund. Blackstone Clarus III L.L.C. is the sole general partner of Clarus GP. The sole member of Blackstone Clarus III L.L.C. is Blackstone Holdings II L.P. The sole general partner of Blackstone Holdings II L.P. is Blackstone Holdings I/II GP Inc. The controlling shareholder of Blackstone Holdings I/II GP Inc. is The Blackstone Group L.P. The sole general partner of The Blackstone Group L.P. is Blackstone Group Management L.L.C. Blackstone Group Management L.L.C. is wholly-owned by Blackstone’s senior managing directors and controlled by its founder, Stephen A. Schwarzman.

Each such Reporting Person may be deemed to beneficially own the Common Stock beneficially owned by the Fund, but neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission that any Reporting Person (other than the Fund) is the beneficial owner of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or for any other purpose, and each of the Reporting Persons expressly disclaims beneficial ownership of such Common Stock.

The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person’s cover sheet and was calculated based on the 24,147,025 shares of Common Stock reported to be outstanding as of May 9, 2019 in the Issuer’s Form 10-Q filed with the Securities and Exchange Commission on May 13, 2019.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: May 22, 2019

[AVROBIO, Inc.—Schedule 13D/A]